Temperature measurement of a tire during use on vehicles is difficult. A common method for temperature tire measurement is insertion of a thermocouple into the tire. A thermocouple typically includes a junction of two conductive leads formed from dissimilar metals. The voltage produced by the junction of the two conductive leads is directly proportional to the temperature at the junction according to the well known Seebeck effect. The temperature of the tire at the measurement junction can be determined by measuring the voltage produced by the junction, so long as a reference junction temperature is also known. The depth and angle of insertion of the thermocouple can be controlled so as to place the junction of the thermocouple at the point of interest for temperature measurement.
FIG. 1 illustrates a typical thermocouple 200 embedded into a passage 110 provided in tire structure 100. As illustrated, the rubber material of tire structure 100 surrounds and holds thermocouple 200. Thermocouple 200 includes a measurement junction 205 of dissimilar conductors surrounded by a protective casing 208. Dissimilar conductors 210 and 220 extend out from measurement junction 205 as conductive leads 210 and 220. By commonly known methods, measurement junction 205 has been inserted at a desired depth and angle so as to be located at a point of interest for measurement. Conductors 210 and 220 extend through passage 110 and exit the rubber material of tire 100 at interface 120.
A disadvantage of using thermocouples in the manner discussed above is the significant cyclic stress that can be applied to the thermocouple conductive leads during rotation of the tire. This cyclic stress can be particularly strong when concentrated at the interface where the conductive leads exit the surface of the tire. The stresses applied to the conductive leads can rapidly fatigue the conductive leads, resulting in distorted temperature measurements and eventual failure of the thermocouple.
Thus, there is a need for a tire temperature measurement apparatus and method that overcomes the above disadvantages. While various implementations of tire temperature measurement techniques using thermocouples have been implemented, no design has emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology.